Pet litter boxes, particularly those used for cats and small animals, typically utilize a tray-like structure to provide a reservoir of granular, absorbent litter material for animal access. The traditional method of disposing of the accumulated urine and fecal matter has been to discard the entire contents of the litter box, including unpolluted absorbent litter material.
More recently, however, environmental and economic concerns have lead to the development of quasi-reusable litter material. Thus, when the pet relieves itself, a popular absorbent granular litter material coagulates and forms clumps as urine and other liquid wastes are deposited within the box. These clumps and any fecal matter are then removed by means of an auxiliary sifting device which separates the coagulated/clumped material from the clean litter material which remains in the tray for reuse. Thus, while the art has addressed the selective disposal of contaminated granular absorbent litter material with some success, many residual problems still exist as will be hereinafter discussed.
There are a number of prior patents relating to the disposal of litter from house pets. Among these are U.S. Pat. No. 3,752,120, Pallesi, which issued on Aug. 14, 1973 and teaches a cat litter box comprising a series of three nesting containers, one of which has a foraminous screen-like bottom and two of which have solid bottoms. The user removes the inner, foraminous bottomed container and disposes of the refuse. Then, the user takes the top box containing the gravel and lifts it out of the third box. The screened container is then nested within the empty third box and the gravel is poured into that box over the screen. Finally, the third box containing the gravel, and the screen-like container, are nested within the now empty top box.
U.S. Pat. No. 4,096,827, Cotter, issued Jun. 27, 1978 and teaches a self-cleaning cat waste disposal device. The device comprises a suitcase type structure with substantially identical compartments pivotally connected along one edge and latchable together by a three way handle along an opposite edge thereof. A pivotally mounted screen unit is included between the container compartments and latchable to one or the other by the handle structure. The litter is located in one half and the box is open with the screen latched to the box top. When the cat owner chooses to sift the litter, the box is closed and turned upside down so that the litter falls through the screen and into the opposite compartment while the waste is retained on the screen. The top compartment is then opened, the screen with the refuse is removed and the refuse is discarded. The screen may then be replaced and latched to the structure in superposition to the clean litter.
U.S. Pat. No. 4,190,525, Menzel, issued Feb. 26, 1980 and teaches a litter and refuse receptacle and separator. The device comprises a receptacle and a sifting screen which is detachably mounted to a crank system which allows the user to turn the handle and rotate the screen through the litter and pick up the refuse therefrom. Alternatively, the receptacle is provided with vertically extending slots adjacent the middle of the receptacle to receive a screen therein. With the screen thus placed in the box, the litter is separated from the refuse by raising one end of the box to cause the litter to fall through the screen while catching the refuse thereupon. The screen is then removed and the accumulated refuse discarded. The screen is then reinserted into the box and the box is tipped the other direction so the litter on that side of the screen is passed through the screen to remove refuse therefrom. The screen is then removed and the litter is shifted for further use. A last embodiment in Menzel comprises a box with a screen on the bottom. The screen has handles extending upward. The screen is simply lifted up to remove the refuse and then is pushed back down into the sand.
Finally, U.S. Pat. No. 4,802,442, Wilson, issued Feb. 7, 1989 and teaches a cat litter screening device. This device includes two planar bottom panels of a mesh material whose openings are sized to pass the litter but not the waste. The bottom panels are pivoted together along a central axis and lift means are attached to the sides for moving the panels up and down through the litter. The lift means include handles and side panels which are also of mesh material. In one embodiment the handles are rigid. In another embodiment lock means are provided by which the handles can be moved to a first position down and away from the sides of the litter box and to a second position where they are locked for applying force to move the bottom panels up and down through the litter.
The basic premise of all of these devices, the separation of waste from litter for discarding the waste therefrom, has been employed in various ways through the years with varied degrees of success. All of the devices appear to fall into three main categories, i.e., (a) the nested screening litter box where one box is nested within at least one other box; (b) the double box system having a screen removably placed over one box and where the entire system is inverted to filter the litter; and (c) the sifting device mounted on the bottom under the litter. The present invention relates to category (c) and has been developed to overcome the lingering problem of replacing the screen into the assembly after the waste material has been removed and discarded whereas most of the prior art devices required great exertion to shake the box and soiled litter and frequently involved a soiled sifting device requiring off-site storage until later retrieved to dispose of the then accumulated waste.
The present invention is clearly an improvement over the prior art because it overcomes all of the aforesaid problems as well as eliminates the need for the human caretaker to maintain his/her face in close proximity to the box for an extended period of time while separating the waste from the litter. It further substantially avoids the possibility of scattering both waste and litter material to the surroundings when the screen is drawn up through the litter material to separate the waste therefrom.